sea
noun
siː 
siː 
1 (often the sea) [uncountable] (also literary seas [plural]) (especially British English) the salt water that covers most of the earth's surface and surrounds its continents and islandsto travel by seaa cottage by the seaThe waste was dumped in the sea.The wreck is lying at the bottom of the sea.We left port and headed for the open sea (= far away from land).the cold seas of the Arctica sea voyagea hotel room with sea view see also the high seas, ocean2 [countable] (often Sea, especially as part of a name) a large area of salt water that is part of an ocean or surrounded by landthe North Seathe Caspian Sea 3 [countable] also seas [plural] the movement of the waves of the seaIt was a calm sea.The sea was very rough.4 [singular] sea of something a large amount of something that stretches over a wide areaHe looked down at the sea of smiling faces before him.Idioms
at sea
1 on the sea, especially in a ship, or in the seaIt happened on the second night at sea.They were lost at sea.2 confused and not knowing what to doI'm all at sea with these new regulations.go to sea
to become a sailor
out to sea
far away from land where the sea is deepest
She fell overboard and was swept out to sea.put (out) to sea
to leave a port or harbour by ship or boat
Usage note: sea / oceanIn British English, the usual word for the mass of salt water that covers most of the earth’s surface is the sea. In North American English, the usual word is the ocean: A swimmer drowned in the sea/ocean this morning.The names of particular areas of seas, however, are fixed: the Mediterranean Sea ◇ the Atlantic Ocean.Sea/ocean are also used if you go to the coast on holiday/vacation: We’re spending a week by the sea/at the ocean in June. In North American English it is also common to say: We’re going to the beach for vacation. note at coast